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#videocompression#interframecompression#bitrate

Why Snow and Confetti Ruin YouTube Video Quality

Tom Scott

6.7M subscribers • 29 videos on Hallway

YouTube
  • Recommended by 3 people: 3 on Hacker News.
  • A classic. People kept recommending it from 2020 to 2024.
  • Presented by Tom Scott

Beginner. No background in the topic needed.

10M views10 years ago3 recommendations

Graphics and audioSystems programmingRenderingPerformance and optimization

Tom Scott explains how interframe compression and bitrate limitations cause video quality to degrade during scenes with high motion like falling confetti.

Your sports team wins. The confetti drops. And suddenly, the video quality falls apart. Why? Let's talk about interframe compression, bitrate, and unnecessary green screen effects. I'm at tomscott.com on Twitter at twitter.com/tomscott on Facebook at facebook.com/tomscott and on Instagram as @tomscottgo You might also like: How Green Screen Worked Before Computers: youtube.com/watch?v=msPCQgRPPjI This uses one Creative Commons by-attribution photo, "Sony Trinitron" by Antífama, available here: flic.kr/p/6DBMYn

Why it's here

3 people recommend this

What people say. Widely recommended as the clearest visual explanation of how video compression and interframe coding work.

Rebuff5007on Hacker News • Recommends

On “Tom Scott: After ten years, it's time to stop making videos [video]”

To this day when I have buffering problems with online videos I immediately think about his explainer-demo with confetti 1. Love his work! 1 link to this video
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rocgfon Hacker News • Recommends

On “How Video Works”

I do not know the answer, but I would absolutely shocked if it was streamed as a regular video. To the best of my knowledge, there are many, many optimizations which go into video. This is a pretty good high-level video I came across - link to this video
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jerfon Hacker News • Recommends

On “Apple Vision Pro – Why It May Be Lousy for Watching Movies on a Plane”

…hunk of pixels is more than just adding up the differences, but you can take that as a suitable first approximation for thought. High-quality pixels have minimal deviation from the source material. Low-quality pixels have significant deviation. Tom Scott has a good video where turns up and down the quality live so you can see it in a single video: link to this video The video's resolution never changes, and you could say the video's bit rate never changes (it probably does because adaptive coding saves YouTube a fortune, but conceptually you could say it doesn't), but the quality of the pixels sure does.…
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jdietrichon Hacker News • Mentions

On “Google and LG creates VR AMOLED 120 Hz at 5500 x 3000”

…s frame. A modern compressed video consists mainly of these interpolated frames, with only a minority of frames containing a full image. This interpolation can use data from both past and future frames (B frames) but can also use just the data in previous frames (P frames). This works extremely well most of the time, but there are some edge cases: link to this video link…
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saltmineron Hacker News • Mentions

On “New 2019 MacBook Air features a slower SSD than 2018 model”

For 4k video, H.265/VP9 have better quality at the same file size, or equivalent quality at a smaller file size. Bandwidth usage matters for keeping people on the website and viewing Google's ads, so Google wants to ensure a smooth streaming experience. And since YT compresses so heavily, uploading in 4k increase the quality at lower resolutions (it seems weird but a 4k video uploaded to YT and streamed at 1080p will look better than a 1080p video uploaded to YT and streamed at 1080p). And as xnyan said, high motion video really destroys video quality on YT, this video really shows how bad it can get: link to this video
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eruon Hacker News • Mentions

On “AT&T’s current 5G is slower than 4G in nearly every city tested by PCMag”

Quite a few. Though to be honest, 4k is currently good enough for me, resolution wise. But: even the highest bitrates you get on eg YouTube ain't good enough to show certain scenes nicely. Especially when snow is involved. That's because the video compression algorithms we have don't cope well with that. See link to this video So there's a clear and simple use case for more bandwidth, even if we don't increase resolution.
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anyfooon Hacker News • Mentions

On “YouTubeDrive: Store files as YouTube videos”

That's the thing though, "looks like" breaks down pretty quickly with things that aren't real images. It even breaks down pretty quickly with things that are real, but maybe not so common, images: link to this video So one question would be: Does your image generation approach preserve a higher information density than big enough pixels?
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woobiliciouson Hacker News • Mentions

On “YouTubeDrive: Store files as YouTube videos”

…to encode your data in some way that abuses the P and B frames, and the macro block size of 16x16. Coding theory for the data output at your end is only one side of the coin, the VP9 codec stupidly good compression is a completely different game to wrangle. And I kinda doubt you'll get much better than your estimate of 1% from the original scheme. link to this video…
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jerfon Hacker News • Mentions

On “MP3 vs. AAC vs. FLAC vs. CD”

Some of it is people ask the wrong questions. On a loudness-war-wrecked pop song I may not be able to tell 128Kbps from the original, but on specific content I have been able to tell. I'm not even claiming golden ears or anything; some specific audio content is the audio equivalent of visual confetti 1, and anyone can hear the difference, because the codec isn't even close. And let me underline, I mean, anyone . No special claims being made here. But all in all, that content is relatively rare, and generally transient even in the music they appear in. 1: link to this video
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ReactiveJellyon Hacker News • Mentions

On “Technical Overview of AV1 Spec”

…otion will cause "HDTV blur" as the encoder struggles to describe complex motion with the limited number of bits it's allowed to use. Stuff like static, film grain, particles like snow or rain, those all suck up bits from the same encoding budget. "Why Snow and Confetti Ruin YouTube Video Quality" by Tom Scott probably explains it nicer than I can link to this video This could be a problem for video game streaming, and it could affect the artistic decisions a game studio makes - Drawing a billion tiny particles on a local GPU will look crisp and cool, but asking a hardware encoder to encode those for consumer Internet (or phone Internet) might be too much. I think streamers have run into this problem a…
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u/humodxin r/compsci • Mentions

On “A way to compress videos by alot without losing any quality”

This video may interest you, it explains some of the pitfalls of that technique: link to this video
1View on Reddit